Showing papers on "Hydrofluoric acid published in 1981"
TL;DR: The results suggest that of the two principal components of 'acid rain', HNO3 may be more toxic than H2SO4 and consistent with the hypothesis that F- transport through biological membranes occurs mainly by nonionic diffusion of HF.
126 citations
TL;DR: In this article, a method of self-consistent optimization of a resonating wave fuction is developed and applied to the reaction HF+D?H+FD. (AIP)
Abstract: A method of self‐consistent optimization of a resonating wave fuction is developed and applied to the reaction HF+D?H+FD. (AIP)
61 citations
56 citations
39 citations
TL;DR: In this article, the latent damage trails in Muscovite mica were revealed by etching it in boiling solutions of 6N NaOH and 6N KOH, and the hexagonal etch pits so obtained have been found to go through interesting variations in their size, shape, and geometry with the change of the etching conditions.
26 citations
Patent•
23 Mar 1981TL;DR: In this article, a solution for the one-step etching of a three layer titanium-nickel-copper metallization was disclosed for the patterned etch of sequential layers of titanium, nickel and copper without excessive attack of underlying silicon dioxide layers.
Abstract: A solution is disclosed for the one-step etching of a three layer titanium-nickel-copper metallization. The etch solution comprises about 1.8 to 2.0 moles/liter hydrofluoric acid, about 2.5 to 4.0 moles/liter acetic acid, about 8.7 to 9.0 moles/liter nitric acid, and balance water. Use of the solution permits the patterned etching of sequential layers of titanium, nickel, and copper without excessive attack of underlying silicon dioxide layers.
20 citations
TL;DR: In this paper, anhydrous hydrogen fluoride (AHF) solutions of uranium and neptunium in oxidation states III to VI have been studied and compared with those of aqueous solutions in the gas phase, solid state, or in nonaqueous solvents.
Abstract: Spectra have been recorded for solutions in anhydrous hydrogen fluoride (AHF) of uranium and neptunium in oxidation states III to VI. The spectra for U(III), Np(III), and Np(IV) in AHF are very similar to those in acidified aqueous solution, but that for U(IV) suggests that the cationic species is UF/sub 2//sup 2 +/. The AHF spectra for the elements in oxidation states V and VI are not comparable with those of the formally analogous aqueous solutions, where the elements exist as well-defined dioxo cations. However, the AHF spectra can be related to spectra in the gas phase, in the solid state, or in nonaqueous solvents for each element in its appropriate oxidation state.
18 citations
TL;DR: In this article, a new method was developed for the analysis of oxides, borides and Al3Ti in aluminium, where 20 g samples are dissolved in hydrochloric acid and the solution is filtered and the silicon in the residue is removed by means of hydrofluoric acid.
Abstract: A new method has been developed for the analysis of oxides, borides and Al3Ti in aluminium. 20 g samples are dissolved in hydrochloric acid — nitric acid solution. The solution is filtered and the silicon in the residue is removed by means of hydrofluoric acid. The undissolved phases were identified by X-ray diffraction and Scanning Electron Microscopy; the composition of the particles was determined by use of emission spectrography and X-ray fluorescence and the size distribution of the inclusions by use of the Coulter Counter.
18 citations
Patent•
24 Nov 1981
TL;DR: A process for the preparation of anthraquinone compounds by condensation of phthalic anhydride with a benzene derivative is described in this article, where a mixture of hydrofluoric acid and boron trifluoride is utilized as catalyst.
Abstract: A process for the preparation of anthraquinone compounds by condensation of phthalic anhydride with a benzene derivative wherein a mixture of hydrofluoric acid and boron trifluoride is utilized as catalyst.
17 citations
Patent•
21 Dec 1981
TL;DR: In this article, the reaction is carried out in conditions such that no fluorsulphonic acid or very negligeable amounts of said acid reach the reactor, and that the formation of new amounts of fluorophonic acid is actively prevented in the reactor.
Abstract: In the production of synthetic anhydrous calcium sulphate and pure hydrofluoric acid, fluorspar is reacted with a mixture of sulphuric acid, oleum and a solution providing from the acid washing. Hence, a synthetic calcium sulphate is prepared, containing only the desired low content of CaF2, while the free sulphuric acid is completely neutralized, other desirable compounds being already present. The reaction is carried out in conditions such that no fluorsulphonic acid or very negligeable amounts of said acid reach the reactor and that the formation of new amounts of fluorsulphonic acid is actively prevented in the reactor. To this effect, on one hand the compounds CaF2 and the mixture-acid are introduced at a high temperature in the reactor and on the other hand the reactor is brought to a temperature such that the reaction initiates at about 100 C, thereby preventing the formation of new amount of fluorsulphonic acid. The gases coming out from the reactor are, in a first step, dried at a high temperature, then dusts are removed therefrom and finally in the last step, the gases are cooled.
14 citations
Patent•
18 Nov 1981
TL;DR: A method of activating titanium surfaces for subsequent cladding with metallic coatings by the steps of wet-blasting, etching and activating, the activating being effected with a solution of chromic acid, hydrofluoric acid and hexafluosilicic acid as discussed by the authors.
Abstract: A method of activating titanium surfaces for subsequent cladding with metallic coatings by the steps of wet-blasting, etching and activating, the activating being effected with a solution of chromic acid, hydrofluoric acid and hexafluosilicic acid.
Patent•
01 Jun 1981
TL;DR: In this article, a mixture of sulphuric acid and hydrofluoric acid, preferably diluted, is used to insolubilise the calcium in the form of calcium sulphate and to solubilize the niobium and/or the tantalum in the forms of oxyfluoride and thus to prevent the formation of appreciable quantities of calcium fluoride.
Abstract: The ore is treated directly and without pretreatment, with a mixture of sulphuric acid and hydrofluoric acid, preferably diluted, so as to insolubilise the calcium in the form of calcium sulphate and to solubilise the niobium and/or the tantalum in the form of oxyfluoride and thus to prevent the formation of appreciable quantities of calcium fluoride. The source of hydrofluoric acid consists above all of the reaction product of CaF2 with sulphuric acid. The niobium and/or tantalum oxyfluoride obtained by the this treatment is treated by liquid-liquid extraction and is optionally converted into oxide. Application especially to the treatment of pyrochlore.
Patent•
BP1
TL;DR: The activity of cation-exchangeable layered clay or crystalline aluminosilicate catalyst in esterification, etherification, hydration, and cracking reactions is promoted by addition of a strong acid such as sulphuric acid, phosphoric acid, hydrochloric acid or para-toluene sulphonic acid as discussed by the authors.
Abstract: The activity of cation-exchangeable layered clay or crystalline aluminosilicate catalyst in esterification, etherification, hydration, and cracking reactions is promoted by addition of a strong acid such as sulphuric acid, phosphoric acid, hydrochloric acid, hydrofluoric acid or para-toluene sulphonic acid. The further addition of water to the reaction can extend the life of the clay catalyst and in some cases its catalytic activity.
Patent•
13 Jul 1981TL;DR: In this paper, anodic etching is used to activate surfaces of superalloys and stainless steels prior to electroplating a metal such as chromium thereon, whereby a metal deposit having excellent adhesion to the substrate is obtained.
Abstract: Process for activating surfaces of superalloys and stainless steels prior to electroplating a metal such as chromium thereon, whereby a metal deposit having excellent adhesion to the substrate is obtained. The article is activated by anodic etching in a novel activation solution containing about 55% to 80% by volume of H 2 SO 4 and about 1% to 10% by volume of commercial 52% hydrofluoric acid, preferably an aqueous bath containing 65% by volume of 95-98% H 2 SO 4 and 5% by volume of 52% hydrofluoric acid at 30 A/dm 2 and 20° C. for one minute.
Patent•
BP1
TL;DR: The activity of cation-exchangeable layered clay or crystalline aluminosilicate catalyst in esterification, etherification, hydration, and cracking reactions is promoted by addition of a strong acid such as sulphuric acid, phosphoric acid, hydrochloric acid or para-toluene sulphonic acid.
Abstract: The activity of cation-exchangeable layered clay or crystalline aluminosilicate catalyst in esterification, etherification, hydration, and cracking reactions is promoted by addition of a strong acid such as sulphuric acid, phosphoric acid, hydrochloric acid, hydrofluoric acid or para-toluene sulphonic acid. The further addition of water to the reaction can extend the life of the clay catalyst and in some cases its catalytic activity.
Patent•
04 Mar 1981TL;DR: In this article, a continuous process for the preparation of trifluoromethylbenzenes from the corresponding trichloro- or tribromo-methylbenenes with hydrofluoric acid is described.
Abstract: This invention relates to a continuous process for the preparation of trifluoromethylbenzenes from the corresponding trichloro- or tribromo-methylbenzenes with hydrofluoric acid. The process is characterized by passing an ascending stream of gaseous hydrofluoric acid, countercurrently through a plurality of mobile successive liquid layers of the trichloro- or tribromo-methylbenzenes.
TL;DR: In this paper, the amount of silicon removed by dilute hydrofluoric acid was measured by inductively-coupled plasma atomic emission spectrometry, down to 1018 atoms Sb cm-3.
Patent•
31 Jul 1981
TL;DR: The activity of cation-exchangeable layered clay or crystalline aluminosilicate catalyst in esterification, etherification, hydration, and cracking reactions is promoted by addition of a strong acid such as sulphuric acid, phosphoric acid, hydrochloric acid or para-toluene sulphonic acid as discussed by the authors.
Abstract: The activity of cation-exchangeable layered clay or crystalline aluminosilicate catalyst in esterification, etherification, hydration, and cracking reactions is promoted by addition of a strong acid such as sulphuric acid, phosphoric acid, hydrochloric acid, hydrofluoric acid or para-toluene sulphonic acid. The further addition of water to the reaction can extend the life of the clay catalyst and in some cases its catalytic activity.
TL;DR: In this article, the extraction of niobium, tantalum and some other elements by diantipyrylmethane (DAM) and hexyldiantipryryl methane from hydrofluoric acid has been investigated in detail.
TL;DR: In this paper, an improved non-dispersive atomic fluorescence spectrometric determination of arsenic by sodium tetrahydroborate reduction is described, and a new burner on which a small argon-hydrogen-entrained air flame can be maintained at a low hydrogen flow rate (0.15 1 min-1) is reported.
TL;DR: In this article, it has been shown that up to at least 0.6 g solid pieces of various samples of hot pressed and reaction bonded silicon nitride can be decomposed in a mixture of 3 mL hydrofluoric acid and 1 mL nitric acid overnight at 150 C in a Parr bomb.
Abstract: An accurate chemical characterization of silicon nitride has become important in connection with current efforts to incorporate components of this material into advanced heat engines. However, there are problems concerning a chemical analysis of bulk silicon nitride. Current analytical methods require the pulverization of bulk specimens. A pulverization procedure making use of grinding media, on the other hand, will introduce contaminants. A description is given of a dissolution procedure which overcomes these difficulties. It has been found that up to at least 0.6 g solid pieces of various samples of hot pressed and reaction bonded silicon nitride can be decomposed in a mixture of 3 mL hydrofluoric acid and 1 mL nitric acid overnight at 150 C in a Parr bomb. High-purity silicon nitride is completely soluble in nitric acid after treatment in the bomb. Following decomposition, silicon and hydrofluoric acid are volatilized and insoluble fluorides are converted to a soluble form.
TL;DR: In this article, cyclical bifurcated hydrogen bonded structures are proposed for aqueous solutions of hydrofluoric acid and for the bifluoride ion which are consistent with the spectral data.
Abstract: Cyclical bifurcated hydrogen bonded structures are proposed for aqueous solutions of hydrofluoric acid and for the bifluoride ion which are consistent with the spectral data. The structure proposed for HF is also applicable to solutions in organic solvents. Raman spectra of tetramethylguanidinium perchlorate suggest that the corresponding Raman spectra of perchloric acid solutions may not be interpreted in terms of a completely dissociated acid. Other evidence including activity coefficient, heat capacity and partial molal volume data suggest that there is some association in relatively dilute perchloric acid solutions between the perchlorate ion and the hydrated proton. This association decreases in concentrated aqueous solutions.
Patent•
15 May 1981
TL;DR: In this article, a surface treatment was carried out by dipping the melt-struck connection part of the optical fiber in a treating liquid of strong acid and then in a treatment liquid of hydrofluoric acid.
Abstract: PURPOSE:To increase the mechanical strength of a connected optical fiber, by carrying out a surface treatment by dipping the melt-struck connection part of the optical fiber in a treating liquid of strong acid and then in a treating liquid of hydrofluoric acid. CONSTITUTION:A treatment liquid 6 of a mixture solution consisting of 1 or >=2 kinds of strong acid such as sulfuric acid, hydrochloric acid, nitric acid, etc. is stored in a liquid tank 7. A melt-stuck connection part 5 of end parts 2A and 2B of optical fibers 1A and 1B is dipped in the tank 7. Thus coat residue, dust, metallic particles, etc. sticking to the surface of the part 5 are removed. Then the part 5 is dipped in a treating liquid containing an aqueous solution of hydrofluoric acid, ammonium fluoride, sodium fluoride in a liquid tank 8. Thus the minute flaws on the surface are removed or annealed. As a result, the strength is increased at the part 5.
Patent•
18 Nov 1981TL;DR: In this article, the electroless deposition of nickel coatings on metals and metal alloy is accomplished with aqueous baths which contain 10-50 g/l of a fluorine-containing nickel compound.
Abstract: The electroless deposition of nickel coatings on metals and metal alloy is accomplished with aqueous baths which contain 10-50 g/l of a fluorine-containing nickel compound; 40 to 200 g/l diammonium hydrogen citrate; 20 to 100 g/l ammonium hydrogen difluoride; 5 to 50 g/l 2-hydroxy-4-methyl benzoic acid, (2,4-cresotinic acid); 0.0005-0.05 g/l copper salt; and 10-100 g/l sodium hypophosphite. Nickel fluoride and nickel (II)-hydroxide carbonate dissolved in hydrofluoric acid have been found particularly advantageous. Smooth and uniform, corrosion-resistant coatings are obtained also on complicated formed parts of magnesium and magnesium alloys.
TL;DR: In this paper, the solubility of thorium fluoride in 4, 8, and 13 M nitric acid solutions was measured as a function of fluoride concentration at 25, 50 and 100°C.
Patent•
26 Nov 1981
TL;DR: In this paper, an aqueous soln. of a mineral acid having ≥ 5% concn. is added to fine α-type silicon nitride powder, and the powder is treated under heating.
Abstract: PURPOSE: To remove iron, calcium, silicon and silicon oxide as impurities from fine α-type silicon nitride powder by treating the powder with a mineral acid having a prescribed concn. or by further treating the treated powder with a mixed acid consisting of hydrofluoric acid and nitric acid under heating. CONSTITUTION: An aqueous soln. of a mineral acid having ≥5% concn. is added to fine α-type silicon nitride powder, and the powder is treated under heating. The soln. is then separated from the treated powder. After further adding an aqueous soln. of a mixed acid consisting of hydrofluoric acid and nitric acid to the powder, the powder may be treated again under heating. Thus, iron, calcium, silicon and silicon oxide as impurities are removed from the α-type silicon nitride. COPYRIGHT: (C)1983,JPO&Japio
Patent•
17 Jul 1981
TL;DR: In this article, an insoluble silicon carbide component is separated and collected by decomposing an analysis sample such as mill scale, iron powder on the like by the use of acids, and the silicon carbides is secured to a filter paper to measure the concentration of the carbide by a fluorescence X-ray analysis.
Abstract: PURPOSE:To perform a rapid quantitative analysis, by a method wherein an insoluble silicon carbide component is separated and collected by decomposing an analysis sample such as mill scale, iron powder on the like by the use of acids, and the silicon carbide is secured to a filter paper to measure the concentration of the silicon carbide by a fluorescence X-ray analysis. CONSTITUTION:Iron powder, weighed and placed in a beaker, is decomposed by heating with hydrochloric acid, and nitric acid is further added to dissolve iron powder by heating. After cooling, supernatant fluid is drained, perchloric acid is then added and heated to produce perchloric acid white smoke. After cooling, water is added to the residue to drain supernatant fluid, nitric acid, hydrofluoric acid and perchloric acid are added for heating to volatilize a silicon compound other than silicon carbide. After water is added to residue, the mixture is washed with hot water several times to collect silicon carbide. The silicon carbide is uniformly dispersed on a filter paper, and a polyvynil alcohol solution is sprayed to cause the silicon carbide to adhere. Then, a fluorescence X-ray analyzer measures to find a silicon carbide content.
Patent•
02 Jan 1981
TL;DR: In this article, an aqueous base coat composition utilizing magnesium ion preferably in conjunction with at least some compounds from the group hydrofluoric acid, phosphoric acid and tannic acid, and exhibiting a pH of less than 7.
Abstract: Described is an aqueous base coat composition utilizing magnesium ion preferably in conjunction with at least some compounds from the group hydrofluoric acid, phosphoric acid, tannic acid, and nitric acid and exhibiting a pH of less than 7. The anti-corrosion and adhesive properties of this base coating composition allow it to be further coated with organic film formers, varnishes, lacquers, inks, etc. to form a finished product which is resistant to corrosives, humidity, impact problems, and chipping.
Patent•
11 Aug 1981
TL;DR: In this article, a pyridine compound of hydrofluoric acid represented by Py(HF)n (n is 1-4) is reacted with sulfur dichloride in the presence of a mixed solvent of methylene chloride and trichlorotrifluoroethane or the like to form sulfur tetrafluoride.
Abstract: PURPOSE:To inexpensively manufacture sulfur tetrafluoride of high purity in a high yield by reacting a pyridine compound of hydrofluoric acid having a specified composition with sulfur dichloride and circulating a compound obtd. by reacting a by- product pyridine compound of hydrochloric acid with hydrofluoric acid. CONSTITUTION:A pyridine compound of hydrofluoric acid represented by Py(HF)n (n is 1-4) is reacted with sulfur dichloride in the presence of a mixed solvent of methylene chloride and trichlorotrifluoroethane or the like to form sulfur tetrafluoride. A by-product pyridine compound of hydrochloric acid is then reacted with a sufficient amount of hydrofluoric acid to eliminate the hydrochloric acid. This reaction product is distilled under reduced pressure to eliminate hydrofluoric acid until Py(HF)1-4 is prepared, and the resulting Py(HF)1-4 is circulated to the reaction with sulfur dichloride.
Patent•
26 Sep 1981
TL;DR: In this article, the etching soln for silicon and silicon oxide films contains, by volume, 0.1W65%, especially 2W50% hydrofluoric acid and 0.01W5% surfactant.
Abstract: PURPOSE: To enable patterning of high accuracy by preparing a mixed soln. contg. hydrofluoric acid and a surfactant and by optionally adding acetic acid or nitric acid. CONSTITUTION: This etching soln. for silicon and silicon oxide films contains, by volume, 0.1W65%, especially 2W50% hydrofluoric acid and 0.01W5% surfactant. As the surfactant an anionic surfactant, a cationic surfactant, an amphoteric surfactant or a nonionic surfactant is used. To further increase the etching effect 0.05W95vol% acetic acid and/or nitric acid may be added to the etching soln. COPYRIGHT: (C)1983,JPO&Japio